Continuous glass yarns are normally provided with a twist which facilitates their use in various textile operations such as covering, braiding and weaving. To obtain such a yarn utilizing current techniques, it is necessary to proceed in three stages.
The initial step comprises the preparation of a coil formed of at least one yarn, which is itself made up of a large number of fibers mechanically drawn from molten glass streams. Generally, these fibers are coated with a sizing in an aqueous solution. In a second step, a portion of the water is eliminated from the coil by drying or upon storing the coil for a period of time. The third step comprises placing the coil on a spinning machine, unwinding the yarn and subsequently imparting to it a single twist before winding it up in this condition on a suitable support.
These operations require a substantial investment of time and energy, together with the purchase of various types of equipment as well as the requirement of procuring a location for installing the equipment. The start-up costs required for the construction of such a production line are particularly high and the cost of the yarn thus produced is therefore greatly increased. A simplification of the prior art process, i.e., by reducing, for example, the number of operations required to arrive at the desired product, would exhibit an immediate economic advantage.
Giving a twist to the yarn imparts to it a greater integrity due to a better cohesion of the fibers which form the yarn, i.e., better than in the fibers of an ordinary yarn. This quality makes it possible to envisage other applications for which the single yarn twist may be used, for example, as a continuous yarn mat or as cut yarn. In applications related to the field of textiles, a process such as that disclosed herein which would make it possible to achieve in a single step the production of a yarn having a single twist would constitute a considerable improvement to presently utilized techniques.
The method disclosed in U.S. Pat. No. 3,250,602 is one example of such an application in this field. Glass yarns are generally drawn from stationary spinnerets supplied with cold glass, in the form of balls, for example, or with molten glass coming directly from a melting furnace. Conversely, the process disclosed and claimed by the '602 patent comprises mechanically drawing a plurality of glass fibers from molten glass streams flowing from a multiplicity of orifices drilled at the base or at the periphery of a rotary spinneret.
Due to the effect of the resultant centrifugal forces, the fibers separate from the axis of rotation of the spinneret as soon as they are formed. They are then gathered below the spinneret by an assembly loop. At this location, the fibers are formed into a yarn due to a twist imparted by the rotation of the spinneret, which directly gives rise to a single twist yarn.
The process of the '602 patent; however, requires an installation which must exhibit very particular characteristics, particularly for the spinneret, which must support very high rotation speeds without deforming too quickly. Additionally, such an installation may be used only for the production of a yarn having a single twist.